Major-General Hugh Trenchard, the RFC commander in France, stated on 10 Apr '17: “The utmost vigour must be shown by all pilots and observers.” This policy worked over the Somme in 1916 but changes in the balance of power in early 1917 eliminated many RFC advantages. 
At Arras we see the genesis of the modern air campaign. Underpinned by Trenchard’s offensive concept, the air battle was more nuanced than generally acknowledged. By 1917 the ground and air battles were inextricably linked.
Protecting artillery-spotting aircraft was the central mission of the RFC. As well, aerial recce provided crucial information for the army, German kite balloons were destroyed, blinding them, and bombing isolated the battlefield, disrupted logistics, and hassled enemy aerodromes.
The RFC made a significant contribution to the outcome of the Battle of Arras. Contact flights tracked troop progress, aircraft directed artillery fire, and Germans behind the lines were MG'd and bombed. This was all made possible by the fight for air superiority.
In addition to fighting the Germans, Trenchard fended off attempts by army commanders such as Rawlinson and Horne who wanted to take control of air resources. Trenchard, with Haig's support, deflected these arguments by showing that the RFC did more than just arty spotting.
Unfortunately for the RFC, there were significant changes in the balance of power between the Summer of 1916 and the Spring of 1917. The German air service steadily improved their technological superiority in the air throughout the Somme campaign.
Other changes included British pilots being sent to the front with less training and the German Air Service changing from its previous defensive posture to the use of Jagdstaffeln (hunting squadrons) with their best pilots to seek and destroy enemy scouts and two-seaters.
In April, the British did enjoy a quantitative, if not qualitative, advantage in fighting machines (465 to 195). And, reinforcements in the form of better aircraft (SE 5 and Bristol Fighter) were on the way.
Trenchard's plan at Arras was nuanced and flexible to control the air space and permit the essential tasks of artillery spotting and reconnaissance to proceed unhindered.
The high casualties of "Bloody April" arose due to a confluence of uncontrollable factors rather than the application of rigid and unimaginative tactics by the Trenchard and the RFC.
Air operations at Arras began on 5 April. Trenchard intended to isolate the battlefield through medium and long-distance bombing attacks, slow the German ability to move reserves, and draw anti-aircraft guns and fighters from the front lines to protect critical infrastructure.
There is no indication that these attacks proved anything more than a minor annoyance to the Germans, but they demonstrate the evolution of British thinking about how to conduct an air campaign at the operational level.
The ground assault started on 9 April. The RFC intent was to control German airspace over the battle area. When working, this program was very successful. Unfortunately, it was difficult to maintain due to pilot and machine shortages, weather, wastage, and air crew limitations.
Despite the heavy losses in men and machines the RFC was able to reinforce its squadrons and increase its net strength in the field. This was also a qualitative improvement as it was largely obsolete types that were destroyed were replaced by top-of-the-line aircraft.
Though the cost was great, the RFC effectively supported the army throughout the battle. Haig said the success of the artillery and infantry during the Arras offensive rested entirely on the efforts of the army coop squadrons of the RFC, who relied on the scouts for protection.
Apr '17 was the costliest month of the war for the RFC but marked the turning point for air ops. The RFC was learning how to effectively fight an air campaign: reconnaissance, arty spotting, interdiction, air superiority, and trench strafing were orchestrated to great effect.
If you want to read more about the Air Battle of Arras 1917, have a look at my article in the British Journal for Military History:
bjmh.gold.ac.uk/article/view/7…
Thanks for reading!
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bjmh.gold.ac.uk/article/view/7…
Thanks for reading!
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